Mechanical hand



June 16, 1953 G. B. ROBINSON MECHANICAL HAND Filed July 5, 1952INVENTOR: George B Rob/17500 MM Af/orneys Patented June 16, 19532,641,769 MECHANICAL HAND George B. Robinson, Napa, Calif. ApplicationJuly 3, 1952, Serial No. 297,191

6 Claims. (01. 3-121) (Granted under Title 35, U. S. Code (1952),

sec. 266) 1 The invention described herein may be manufactured and usedby and for the Government of the United States of America forGovernmental purposes without the payment of any royalties thereon ortherefor.

This invention relates to prostheses and, more particularly, to anartificial, mechanical hand.

Prior art artificial hands usually suffered from the deficiencies ofbeing quite complicated mechanically, thus requiring frequent repair,and failing to provide means for equalizing the grip of the severalfingers. An object, therefore, of the present invention is to provide anartificial hand of relatively simple construction in which the grip ofthe various fingers is automatically equalized to facilitate grippingirregular objects.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description 'when considered inconnection with the accompanying drawings wherein:

Fig. l is aview of the dorsal aspect of a preferred embodiment of thisinvention;

Fig. 2 is a lateral side view of the mechanical end of Fig. 1, partiallybroken away to show details of the operating mechanism; and

Fig. 3 is a sectional view taken along the line 33 of Fig. 1 showing thephalange actuating arrangement.

Reference is now made to the drawings wherein the numeral l indicatesgenerally the wrist of the artificial hand, including a U-shaped metal'member 2 having a threaded extension 4 for attaching the wrist to abucket or socket applied to the stump of the amputee, and having rigidlyattached thereto also a supporting arm 6. Attached to the Wrist by meansof screws 8 are flexible mounts I6, made of laminated rubber and fabricmaterial to carry the metacarpal pieces l2 which are attached thereto byscrews 14. Spacers 6 keep the metacarpals in their proper relation toeach other. The metacarpal of the thumb'is fastened with a similarrubber-fabric laminate I8 to the rubber mount of the forefingermetacarpal bymeans of screws 20. Each of the four fingers includes twophalanges generally indicated at 22 and 24, the first phalange beingarticulated as at 26 to its corresponding metacarpal and the secondphalange being articulated as at 28 at its proximal end to itscorresponding first phalange. The thumb member is comprised of themetacarpal 30 carried by the laminated mount 18 and further supported insomewhat extended position by a similar laminated bridge 32, attached tothe distal palmar region of the metacarpal of the middle finger as by ascrew 34. The single phalange of the thumb is articulated at 36 to themetacarpal of the thumb.

The actuating mechanism for simultaneously flexing the fingers and thumbcomprises a system of cables. opposite ends of which are anchored atcorre- This; system includes a first cable 38,

2 sponding points to the distal regions of the first phalange of theforefinger (as at 39) and the first phalange of the middle finger. Thesystem also includes a second cable 40, the opposite ends of which aresimilarly anchored to the distal regions of the first phalange of thering finger and the first phalange of the little finger. The cables passaround pulleys 42 and 44, respectively, carried by an equalizer bar 46-pivoted at 48 on a short link 50, which, in turn, is pivoted at 52 to alever 53, which, in its turn, is pivoted to the supporting arm't at 54.The bar it operates as an equalizer to permit all fingers to flexsimultaneously different amounts if necessary, The thumb is actuated bya cable 55 anchored at 56 to the intermediate region of the phalange ofthe thumb member and passing through a, sheath 58. which extends throughan aperture in the bridge 32 and thence through an aperture (not shown)in the metacarpal piece of the middle finger, terminating at its otherend at an anchored point 60 on the lever arm 6. At the distal i endoflever 53 a cable 62 is fastened by means of articulated fitting 64. Thecable 62 is adapted for. connection to any of the conventionalhand-operating cables ordinarily supplied with artificial arms, such asa cable arranged for actuation by a harness responsive to shrugging ofthe shoulder of the amputee.

To permit motion of the lever arm 53 with its equalizer bar mechanismunder the action of cable 62, the metacarpal pieces are each cut away toform a large aperture 66 (Fig. 2). The provision of this aperture servesthe additional purpose of making the metacarpal piece lighter in weight.Despite the material removed to form the aperture, the metacarpal does,however, provide sufficient strength and rigidity'by virtue of itsflanged construction. The material used is preferably aluminum oraluminum alloy or the like. The thumb and fingers are similarly made ofthe same material, also flanged for strength. The thumb phalange 68, forexample, is flanged as evident at 10, and lightened in weight by beingpierced as at 12'. structurally similar to each other, each phalangebeing made generally of two flanged, structural sections, roughlychannel-like, placed back to back and fastened together with spacersbetween them. As seen in Figs. 1 and 2, particularly, the constructionis typified by the forefinger where the first phalange includes themedial structural member 12 and the lateral structural member 14 havingturned-over flanges l6 and 18. The two members 72 and 74 are fastenedtogether by two pins 19 and 80, riveted or spot-welded or the like, Theungual phalange is similarly constructed of a medial member 82 and alateral member 84 flanged as at 86 and 8B, the two members beingfastened together by pin 90 and screw 92. The first phalange isarticulated, as previously described, at 26 to its correspondingmetacarpal,

this being accomplished by means of a screw 94 The other four fingersare .quite sufiicient for the purpose.

larly, the ungual phalange is articulated as at 28 to the first phalangeby means of a screw IOU, Washers I02, and grooved spacer I04.

For causing automatic fiexion of the ungual phalange in response toflexion of the first phalange a cable [66 (Fig. 3) is provided, anchoredat its distal end to the screw 92, passing over the pin 99 and under andtangent to the spacer H34, thence over the spacer 98, finally be-v inganchored at its proximal end to the metacarpal at screw I98. To assistin returning the fingers to an extended position after flexion, a coilspring H8 is provided for each of the four fingers. The spring isanchored at one end [[2 to the ungual phalange, and at its other end I Mto the first phalange. Fora similar purpose, the spring I I6 is providedon the thumb.

Operation In using the illustrated embodiment of the invention, the handis attached to the arm piece of the amputee by means of the threadedconnection 4, the actuating cable 62 is attached to the cable fromamputees shoulder harness and a glove of rubber-like material,preferably simulating a natural hand, is slipped onto the hand. Thisglove is molded in the open position and, when flexed, tends to returnto that position by virtue of its resiliency.

With no tension on the cable 62 the hand remains in a natural-appearingsomewhat extended position, being held in that position by the combinedaction of the resilient glove and the springs It, although the glovealone may be To grip an object the amputee tenses the cable 62 causingthe lever arm 53 to move from the position shown in phantom line in Fig.3 to the solid line position. This moves bodily the equalizer bar 46carried by the lever arm 53 and thus tends to draw the cables 38 and 40to the right, as viewed in Fig. '3, tending to fiex the first phalangeof the fingers attached to those cables. However, by virtue of the pivotat 48 it is possible for one pulley that moved by the other pulley andcable, which condition would obtain if one pair of the four fingersmeets an obstruction sooner than the other pair, as would be the case ingripping irregular objects. Furthermore, of each pair it is possiblethat one finger can move a diiferent distance than the other of thatpair by virtue of the pulleys and the fact that a single cable is anthusbringing the thumb in opposition to the.

other fingers in a natural manner adapted for the gripping of an object.To release the grip on the object, the amputee simply releases thetension on cable 62 and the resilient glove, either alone, as the casemay be, or with the aid of the springs H and H6, restores the hand toextended position.

Obviously many modifications and variations with its cable to move adifferent distance than of the present invention are possible in thelight of the above teachings. It is therefore to be understood thatwithin the scope of the appended claims the invention may be practicedotherwise than as specifically described.

What is claimed is:

1. A hand prosthesis comprising a Wrist; a pluralit'y of metacarpals;resilient means for mounting said metacarpals on said wrist; a pluralityof phalanges articulated to said metacarpals; a second plurality ofphalanges articulated to the phalanges of said first plurality; anequalizer bar pivotally mounted on the hand; a pair of pulleys mountedon said equalizer bar on opposite sides of the pivot axis of said bar; afirst cable passing over one of said pulleys and anchored at one end toone of said first plurality of phalanges and anchored at its other endto a second of said first plurality of phalanges; a second cable passingover said second pulley and anchored at one end to a third one of saidfirst plurality of phalanges and anchored at its other end to a fourthone of said first plurality of phalanges; means for bodily moving saidequalizer bar to apply tension to said cables; and means connectedbetween said metacarpals and said second plurality of phalanges forautomatically flexing said second plurality of phalanges in response tofiexion of said first plurality of phalanges.

2. The prosthesis of claim 1 including a support arm rigid with saidwrist; a lever arm pivoted to said support arm about a lateral-medialaxis; said equalizer bar being pivoted to said lever arm about adorsal-volar axis; the said means for bodily moving said equalizer barineluding a cable connected to said lever arm for rotating said leverarm about said lateral-medial axis and adapted for actuation by thewearer.

3. The prosthesis of claim 2 including a thumb phalangeartioulated toone of said metacarpals; and a cable connected between said thumbphalange and said lever arm whereby said thumb phalange is flexedsimultaneously with fiexion of the finger phalanges.

4. The prosthesis of claim 3 including resilient means for extendingsaid phalanges upon release of tension on said wearer-actuated cable. 5.The prosthesis of claim 1 wherein said first cable is anchored atits'one end to a phalange of the little finger and at its other end to aphalange of the ring finger and wherein said second cable is anchored atits one end to a phalange of the middle finger and at its other end to aphala'nge of the forefinger.

. 6. A prosthesis element including a base member; a first phalangearticulated proximally about a first axis to said base member; a secondphalange articulated to said first phalange about a second axis in thedistal region of said first phalange; a cylindrical guide describedabout said first axis; a cylindrical guide described about said secondaxis; a cable anchored at its one end to said base member, passingdorsally over and in contact with said first guide and thence vOlarlyover and in contact with said second guide and being anchored at itsother end to said second phalange; and a third guide, carried by saidsecond phalange, for maintaining said cable always in contact with saidsecond guide during relative fiexion and extension of said phalanges.

GEORGE E. ROBINSON.

No references cited.

